I've lived in Thailand for over 20 years, and have a Non-Imm Visa Type O. I extend my one-year stay using Retirment qualifications.
I've answered your questions below:
1. Yes, for initial stay extension.
2. Yes, every year.
3. No, you only have to have the THB 800 K in your account for 2 months before and 3 months after you apply for the one-year extension. Your account cannot dip below THB 400 K.
4. Yes, and you have to turn in that map every year, but they only visit you the first time unless you move.
5. I've never been asked to leave my passport at Immigration and would not want to, but if that's what they've told you to do, I'd go ahead and do it. First, take photos of your passport and all the important pages.